RASSF1 and neoplasm: Abnormal hypermethylation in the promoter region of tumor suppressor gene RASSF1A (RAS associated domain family 1 A), repair gene MGMT, apoptosis-related genes EBF3 (Early B Cell Factor 3), cell cycle-related gene CDKN2B (Cyclin-dependent kinase inhibitor 2B) and other important genes often occurs in precancerous lesions or during the early carcinogenesis of tumors, inhibiting transcriptional activity and leading to tumor occurrence (40–42).